The aim of the research plan is to study the genetics of ribosome synthesis and the interaction of ribosomal components during ribosomal functioning, in B. subtilis. Our laboratory has previously shown that most of the DNA base sequences complementary to 5S, 16S and 23S ribosomal rRNA are found in the same region of the subtilis chromosome as several mutations conferring resistance to certain antibiotics which affect ribosomal function. We have subsequently shown that some of these mutations conferring resistance in B. subtilis also cause changes in specific ribosomal proteins or are very closely linked to genes which code for ribosomal proteins. On the basis of this genetic evidence and on various kinetic data dealing with the synthesis of ribosomal components, we postulate that the genetic determinants for rRNA and ribosomal protein are coordinately controlled. To provide evidence for the concept of the ribosomal operons: A. We are mapping the genetic determinants for rRNA and several ribosomal proteins and are mapping markers which confer resistance to ribosomally active antibiotics. B. We are studying the kinetics of rRNA and protein synthesis with cells undergoing dramatic increases in ribosome content per cell (spore germination). In our genetic mapping studies we have demonstrated interactions between ribosomally active antibiotic resistance markers, notably thiostrepton and erythromycin resistance. We are studying this relationship at the genetic, physiological and structural levels, as we believe the interaction is expressed at the ribosomal level, possibly the peptidyl transferase site.